Somatomedin (SM) has been proposed as a mediator of the effects of Growth Hormone (GH). The well known anti-insulin effects of growth hormone in vivo and the insulin-like in vitro effects of SM seem paradoxical. The aim of this project is to examine the state of SM as it is carried in the plasma, and determine its relationship to the purified form of SM. Comparison of the biological effects of SM in the state as it exists in plasma to extracted SM will be made both in vitro and in vivo. This information will help place SM and GH into physiological perspective.